2 Answers
2

On CentOS, I don't get udev messages when I plug in a simple USB thumbstick. Instead I get:

[sdb] Assuming drive cache: write through

a couple of times.

But this isn't udev, or syslog mentioning this to you on the console. You could know this for sure yourself, by killing syslogd or rsyslogd (Please make sure this isn't a production server, which I hope it is not what with inserting USB hubs and all that :) and re-inserting the USB device.

The messages still popup, so as Ulrich mentioned, this is coming from the kernel, or the USB module to be exact, which uses kernel.printk to show you these messages, not using any system services at all.

An excerpt from the linux documentation sysctl/kernel.txt:

The four values in printk denote: console_loglevel,
default_message_loglevel, minimum_console_loglevel and
default_console_loglevel respectively.

These values influence printk() behavior when printing or
logging error messages. See 'man 2 syslog' for more info on
the different loglevels.

console_loglevel: messages with a higher priority than
this will be printed to the console

default_message_level: messages without an explicit priority
will be printed with this priority

minimum_console_loglevel: minimum (highest) value to which
console_loglevel can be set